A common consideration when designing gas turbine power plants, especially for automotive purposes, is to maintain a high efficiency while simultaneously reducing weight and space requirements, and further to make the various components of the plant easily available for survey and maintenance. A further aim is to design the plant in such a manner that the gas producing part can be easily accelerated which is of high importance, especially with automotive plants.
In order to obtain satisfactory operational results the plant should include three turbine rotors connected to their own shafts, a first turbine rotor being drivingly connected to the compressor of the plant, to form a rotor spool. This first turbine rotor is so designed that it, at full load upon the plant, will not provide sufficient power for the compressor work, so additional power will have to be transferred from either of the two other turbine rotors. The second rotor, as counted in the direction of flow of the gases, is the power turbine proper, while the third turbine rotor has diverse auxiliary functions and in a manner known per se is interconnected to the second turbine rotor, the last mentioned rotors operating upon concentric shafts.